This invention relates generally to gas turbine engines and more particularly to exhaust duct liner attachment systems and methods. In gas turbine powered aircraft, it is necessary to protect the exhaust duct with an insulating shield in order to prevent the heated core gases from damaging the exhaust duct. Typically, exhaust ducts are made from titanium or titanium alloys and have temperature limits in the vicinity of 400° F. (˜204.4° C.). Exhausted core gases can reach temperatures upwards of 35000° F. (˜1648.89° C.). It is, therefore, necessary to line exhaust ducts with a material capable of withstanding the peak temperatures of the exhaust gas and that prevents the exhaust duct from reaching its temperature limitations.
For particular operations, particularly in military operations, it is desirable to have aircraft with conventional take-off and landing (CTOL) capabilities, and short take-off vertical landing (STOVL) capabilities. CTOL requires conventional thrusting of the aircraft in the horizontal direction, while STOVL requires thrusting of the aircraft in vertical and intermediate directions. Some dual capability aircraft designs thus employ variable direction exhaust ducts for directing thrust produced by the exhaust nozzle in both the horizontal and vertical directions. Variable direction exhaust ducts typically comprise multiple co-axial exhaust duct segments having angled junctions, whereby the segments can be rotated with respect to each other to redirect the direction of thrust. The exhaust duct segments interface through a swivel bearing joint, which extends partially into the exhaust duct. This has the effect of restricting the diameter of the exhaust duct near the swivel bearing joint. In order to properly pre-load the swivel bearings, it is typically necessary to assemble the exhaust duct segments before attaching exhaust duct liners to the exhaust duct segments. Exhaust duct liners must have an outer diameter that allows them to pass through the restricted inner diameter resulting from the presence of the bearing joints in the assembled exhaust duct. It is, therefore, necessary to have an exhaust duct liner suspension system that spans the distance between the exhaust duct and exhaust duct liner, while also being insertable past the bearing joints. Various systems and methods can be employed to attach duct liners to exhaust ducts for both conventional and variable exhaust ducts, such as three bearing swivel ducts (3BSDs). It is desirable to increase the performance of these suspension systems, such as reducing vibration, while also reducing their cost and weight.